A zero carbon building is a building with zero net energy consumption or zero net carbon emissions on an annual basis. In recent years, low/zero carbon buildings have attracted much attention in many countries because they are considered as an important strategy to achieve energy conservation and reduce greenhouse gases emissions. Located at the heart of Kowloon Bay, the upcoming vibrant premier business district in Hong Kong, ZCB is a green oasis in a densely populated urban area.
ZCB is the first Zero Carbon Building in Hong Kong. Developed by the Construction Industry Council in collaborating with the Hong Kong Government, it aims to showcase the state-of-the art eco-building design and technologies to the construction industry locally and internationally and to raise community awareness of low carbon living in Hong Kong. (HKCIC, 2012)
This ZCB generates on-site renewable energy from photovoltaic panels and a tri-generation system using biofuel made of waste cooking oil and achieves zero net carbon emissions on an annual basis. Beyond the common definition of a ‘zero carbon building’, ZCB exports surplus energy to offset embodied carbon of its construction process and major structural materials.
The building has been designed passive as well as active systems to avoid emitting carbonaceous substances, here are some of the main systems:
Wind catcher is a device that ventilates a building by the use of wind. A small tower on the roof contains an opening that faces the prevailing wind, which is at a cooler temperature than the interior of the building. Because the wind velocity at this opening is greater than it is at the lower windows of the building, air in the shaft of the tower is forced down the shaft to cool the building.
High Performance glazing
The high performance glass wall system offers good thermal and optical performance to lower cooling load, reduces the reliance on artificial lighting and hence reduce energy consumption. The reflecting shade inside the glazing achieves this by reflecting heat and reducing heat again.
High-volume-low-speed fans can generate high volume of air flow at a low speed. The noise associated with the movement of the fan blades is low. These huge ceiling fans move large volumes of air effectively by using their patented blade design, which enhances evaporation for comfort. The fan can effectively reduce the necessary duration of air conditioning.
The active skylight is a roof window frame set with inclined shading fins. The skylights can be shaded if necessary to optimize daylighting and solar control. The shading fins are controlled by computer software and sensors by adjusting their shading angles to cut out direct sunlight at different angles as the sun passes over the building. They diffuse daylight into the interior as needed, greatly reducing the heat gain from direct sunlight.
In the ZCB, renewable energy is generated on site from solar energy by photovoltaic (PV) panels and from biofuel (one kind of biomass) made of waste cooking oil.
-Main facade facing south-east for higher potential to capture prevailing summer breeze
-Tapered built form to create larger pressure differences on different building facades to draw stronger air flow across the building
-High headroom for key spaces to enhance stack ventilation effect
-Natrually ventilated design at entrance to enhance ventilation effect
Based on the above designs and technologies, the ZCB consequently does not increase the amount of greenhouse gases in the atmosphere. It does at times consume non-renewable energy and produce greenhouse gases, but at other times reduce energy consumption and greenhouse gas production elsewhere by the same amount, that’s why it introduce all these systems to achieve the goal of zero-carbon emission.
ZCB Experience, viewed 30 May 2015, <http://zcb.hkcic.org/Eng/Features/map.aspx>
Tim Smedley, 2013, ‘Can zero-carbon buildings become a reality?’, The Guardian, viewed 30 May 2015, <http://www.theguardian.com/sustainable-business/can-zero-carbon-buildings-become-reality>